you do not need to have this key.. the door that this key opens can be picked by bards and rogues. this ONLY applies to the north WING key. you still must have a palace key and north TOWER key to progress through the zone as those doors cannot be picked.

A trick I use and you can use it on just about any locked door is 1) shrink to smallest size 2) run into door and find the point where you stop moving 3) hit a potion of minor translocation ( you may have to repeat this step many times)